Field
One or more embodiments relate to composite cathode active materials, cathodes and lithium batteries including the same, and methods of preparing the composite cathode active materials, and to composite cathode active materials having a reduced amount of lithium remaining on the surface thereof, high initial capacity, high rate capability, and long lifespan, cathodes and lithium batteries including the same, and methods of preparing the composite cathode active materials.
Description of the Related Technology
Lithium batteries, particularly, lithium ion batteries (LIBs) have been used as a power source of portable electronic devices due to high energy density and design efficiency. Recently, as lithium ion batteries have been used as power sources of electronic vehicles or power storage in addition to portable electronic devices, much research into materials for lithium ion batteries having high energy density and long lifespan has been conducted.
Among these materials, Li—Co oxides, such as LiCoO2, have been widely used as cathode active materials. However, due to maldistribution and scarcity of cobalt, a stable supply thereof may not be guaranteed and manufacturing costs increase.
Thus, Li—Ni composite oxides or Li—Mn composite oxides instead of expensive Co have been developed as cathode active materials. Particularly, research into Li—Ni composite oxides is increasing in order to jump over limitation of Li—Mn composite oxides in light of a price, a stability, and a capacity.
However, since a large amount of lithium is deintercalated from the Li—Ni composite oxides during charging, the Li—Ni composite oxides have unstable structures which relatively easily collapse with respect to Li—Mn composite oxides, and capacity thereof deteriorates relatively severely during charging and discharging. Furthermore, since oxygen may also be deintercalated simultaneously when lithium is deintercalated from the cathode active material, capacity of the cathode active material may deteriorate, and the cathode active material may have relatively low thermal stability due to reaction with an electrolyte with respect to Li—Mn composite oxides.
Therefore, there is a need to stabilize the Li—Ni composite oxides to improve battery performance by reducing an amount of residual lithium therein and inhibiting side reactions between the composite cathode active material and an electrolyte.